1. Field of the Invention
The present invention relates to an ink cartridge suitable for mounting on a carriage carrying an ink jet type recording head.
2. Related Art
An ink jet printer is constructed in such a way that an ink jet type recording head--wherein pressure is applied to pressure-generating chambers communicating with a common ink chamber and nozzle apertures, and ink is discharged from nozzle apertures--and an ink cartridge supplying ink to a recording head-are mounted on a carriage; and -ink drops matching printing data are discharged onto a recording sheet while the carriage is moved reciprocally.
Incidentally, because the nozzle apertures of the recording head are positioned in a location lower than the liquid level of the ink cartridge, and positive pressure acts on the nozzle apertures, normally a porous flexible member such as foam rubber is accommodated within the ink cartridge and it is constructed in such away that due to surface tension from the porous flexible member the pressure in the ink cartridge is a little lower than that in the nozzle apertures; and measures are taken to prevent ink bleeding from the nozzle apertures.
However, when ink consumption continues, the amount of ink absorbed in the porous flexible member becomes less and the capillary force of the porous flexible member becomes greater; the supply of ink to the recording head becomes easily delayed, the ink within the cartridge is not completely consumed and the actual volume of the porous flexible member only makes the ink cartridge larger because the amount of ink which can be accommodated in the cartridge becomes smaller.
In order to solve these kinds of problems, inventions have been considered utilizing ink accommodated in a bag member maintaining negative pressure by normal expansion force being supplied by a flexible member, wherein the bag member is mounted on a base with ink being supplied to a recording head through a tube as disclosed in Unexamined Japanese Patent Publications Nos. Sho. 56-67269, and Hei. 6-183023 etc. However, because members such as springs etc. for generating negative pressure are necessary, the size becomes larger, and also because changes in pressure occur caused by ink oscillation due to the movement of the carriage, and there is the problem that it is not suitable to mount them in the carriage.